As you were saying, the precursors have already been dealt with in the Controlled Drugs and Substances Act through precursor control regulations.
My question was, why treat these precursors as special and up it into a law, if you can already deal with them? More importantly, if it's important to do it, why wouldn't you do it with the precursors to all drugs? Someone might try to get out of a court case by saying it's not constitutional; that they're not being treated equally, because you can get the precursors for these other drugs—ecstasy or whatever—and not face the same charge: it's not illegal.